| （英） |
Recently, lighting-constrained visible light communications (VLCs) have attracted much attention. This is due to the depletion of radio frequency resources and the widespread use of light-emitting diodes (LEDs). One of the modulation schemes for lighting-constrained VLCs, digital color shift keying (DCSK), capable of mitigating the effects of LED nonlinear emission, was proposed. To further enhance the channel capacity per LED in DCSK systems utilizing multiple RGB-LEDs, spatially modulated DCSK (SDCSK), which combines DCSK with spatial modulation (SM), has been proposed. SDCSK modulates both color information (DCSK symbols) and spatial information (SM symbols) according to the transmitted data, allowing independent demodulation of each symbol at the receiver. However, at transceiver locations with high channel correlation, the demodulation of SM symbols becomes challenging. This paper proposes a power-imbalanced SDCSK (PI-SDCSK) method, which employs power imbalance, an effective technique for SM systems under high channel correlation. Specifically, we implement power imbalance by adjusting the transmit pulse width to maintain the linear emission of LEDs in DCSK. Furthermore, we derive the discrete-input continuous-output memoryless channel (DCMC) capacity of 8-DCSK and 8-SM-based PI-SDCSK, and compare it with conventional SDCSK. The results demonstrate that at transceiver locations with high channel correlation, the DCMC capacity of PI-SDCSK improves by up to 3 bit/s/Hz compared to conventional SDCSK. |